Vacuum cleaners



April 24, 1956 P. PREIS 2,743,054

VACUUM CLEANERS Filed Aug. 12. 1952 m/mwmq; PAUL PR5; 5

United States Patent 0 2,743,054 VACUUM CLEANERS Paul Preis, Wuppertal-Elberfeld, Germany Application August 12, 1952, Serial No. 393,896 Claims priority, application GermanyAugust 16, 1951 2 Claims. (Cl. 230-127) This invention relates to vacuum cleaners, and more particularly to vacuum cleaners having a dust collector disposed in the rear of the blower or fan.

In such vacuum cleaners, the dust and dirt sucked in comes into contact with the fan and with the parts leading from the latter to'the dust collector. In designing the fan and the walls of the air guide space in the rear thereof, account must therefore be taken not only of aerodynamic considerations, but also the necessity of smooth, friction-free delivery of the solid particles entrained by the current of suction air. Where these are dust and similarparticles of small size, known vacuum cleaners comply with the requirements imposed on them. But when it is required to suck in parts of greater size, and particularly parts of considerable length, difficulties occur. cloth, or the like, first tend to cling to the front edges of the fan blades, where they become entangled. Even when such a thread has already reached the discharge connection at one end, while its other end is still .near

the fan, this thread will coil up into a spiral, since the air current in the discharge connection is entirely insufficlent to pull the thread out of the fan, which is generally running at high speed. The consequence is that'the thread will either wind itself around the hub of the fan, or will wind itself on to the inner wall'of the annular air guide space following the fan which is provided in this type of vacuum'cleaner. Consideration of compact construction hitherto dictated that this inner wall be made cylindrical. In consequence of this cylindrical shape of the housing following the fan, .the long thread winds itself so tightly around the same,-'that itcannot be detached and removed by the aircurrent. In consequence, in time there is formed a wad or felted mass around this housing wall which chokes the vacuum cleaner and makes it ineifective.

The invention aims at obviating these drawbacks by providing a vacuum cleaner having an annular air passage in rear of the fan and having a dust collector connected by way of a substantially radially disposed discharge connection, which will dependably suck up long particles, suchv as sewing threads, shreds of cloth, orthe like, and pass them dependably into the dust collector.

To this end, according to the present invention, the inner walls of the annular air guide passage following the fan are tapered towards the fan.

Preferably, the Walls are comically tapered and con veniently surround the driving motor for the fan; Due to this tapering the pull acting on a thread drawn in a spiral around the walls is split up into aforce normal to the wall surface and a displacing force perpendicular thereto, i. e. in the direction of a conical surface line, the magnitude of the latter force being dependent on the apex angle of the cone. According to a feature of the invention, this apex angle is so selected that the displacing force is greater than the friction of the thread against the wall resulting from the coefiicient of friction and the normal pressure. The thread tension thuseftects Such parts, such as sewing threads, shreds of 2,743,054 Patented Apr. 24, 1956 of the thread is promoted. If nevertheless the ring of thread or'cloth fragment is not completely sucked off, it has been found that it will then come into contact with the blades themselves, where in consequence of the high speeds it will be torn and broken up. This action is assisted, according to a further feature .of the invention, by the fact that the annular air guide space following the fan is disposed coaxially to the fan and has an approximately pearshaped, widely roundedout cross-section, into which the air coming from the fan enters substantially tangentially. By virtue of this arrangement of the air-and with'it the sucked-in dust and dirt particlesperfonns, apart from the circular movement around the axis of the fan, an additional circular movement around an annular axis running through the annular space, whereby the entrained particles and particularly threads, are carried around in a continuous circling movement, so that they come into the range of. the fan blades, which break them up, and are passed to the discharge connection, through which they can escape into the dust collector.

Not only the air guide walls in rear of th'e fan, but also the fan itself, can however be shaped in accordance with the previously mentioned object. Thus, it is advisable to dispose the front edges of the fan blades generally transversely to the fan axis, in order to prevent threads from being able to cling thereto at all. An arrangement which has been found particularly effective for this purpose is one in which the front edges of the fan blades form an angle of between 45 and90 with the fan axis.

Particular importance is to be attributed to the frictionfree merging of all guide parts into one another. Thus the fan plate may be so embedded in the housing wall surrounding it, that the surface of the plate lies flush with the surface of the housing. By this means, the

winding of the threads sucked in around the fan hub can be reliably avoided. In addition, it is advisable to continue the'preferably conical surface of the fan plate at least a short distance in the housing wall, and from there to allow it to merge through a widely curved edge into the conical wall part of the annular air guide passage.

' In order that the invention may be more readily understood, reference is made to the accompanying drawings, which illustrate diagrammatically and by way of example, one embodiment thereof, and in which: I

Figure 1 shows a vacuum cleaner blower in a vertical longitudinal section;

Figure 2 shows a detail of Figure 1 drawn on a larger scale; and I Figure 3 is a graphic diagram of the forces acting on an entrained particle.

The plate 6 of a fan lies coaxially with a suction connection 4 in a housing and is provided with blades 5. The fan, rotating at high speed, forces the dust-laden air sucked-in through the connection l into an annular air guide space 7, whence it passes through a radially disposed discharge connection 8 passing through the outer housing wall into a dust collector (not shown).

The plate 6 of the fan is slightly conical in shape, the apex of the cone facing the suction connection 4. Behind the fan plate 6 is a likewise slightly conical housing wall 9, in which the fan shaft is mounted and which is recessed to receive the fan plate 6 to such'an extent that the front surface of the plate lies flush with the surface of the housing wall. The slightly conical housing wall 9 is continued a short distance outside the fan plate, and

then merges through a well rounded corner into an annular wall 10 which is in the shape of a truncated cone, with the conical surface of smaller diameter facing the fan 5, 6. The apex angle o of this cone is relatively acute and according to the invention amounts to 10 and more. The driving motor (not shown) for the fan is mounted inside the truncated cone formed by the annular wall 10. The conical wall 10 forms the inner wall of the annular. space 7, which has an approximately pear,- shaped cross-section and into which the air delivered by the fan 5, 6 enters approximately tangentially. Viewed as a whole, therefore, the air sucked in is forced by the fan 5, 6 from the suction connection 4 through the annular gap 11 into the annular space 7 of pear-shaped cross-section, whence it escapes through the discharge connection 8 into the dust collector.

The fan blades 5 effecting the actual movement of the air have front edges 5', which are directed transversely to the fan axis. The angle a formed by the front edges 5' with the fan axis, amounts to between 45 and 90.

The mode of operation of the vacuum cleaner will now be described with reference to a sucked-in thread x. It will be assumed that a thread has been sucked into the fan through the suction connection 4. Owing to the substantially radially directed front edges 5 and the high speed of the fan, which amounts to between 10,000 and 20,000 R. P. M., the thread will not, as hitherto, cling to the fan blades, but will be thrown off into the annular space 7. In favourable cases the threads will pass directly into the discharge connection 8. In the unfavourable case, although one end of the thread will pass into the discharge connection 8, the rear end will still remain near the fan. The latter tends to coil up the thread in a spiral around the housing cone 10. Due to the suction, the thread is under a tension represented by S in Figure 3, which is the resultant of a normal pressure N on the housing and a displacing force P directed along a surface line of the housing. The normal pressure N, in conjunction with the coefficient of friction, determines the friction of the thread on the housing. If this friction is smaller than the displacing force P, the thread will travel on the cone surface in the direction of the fan. The apex angle it determines the ratio of the two forces N and P. It has been found that in order to effect the movement of the thread towards the point of the cone, a cone angle of 10 and more is sufficient. Larger cone angles, which in themselves would be more advantageous, are normally impossible owing to the desirability of a compact construction for the vacuum cleaner.

The thread moving towards the fan 5, 6 through the force component P of the thread tension, thus passes into circles of smaller diameter, whereby it is loosened. In addition, in moving it comes into the range of the inlet gap 11, where its detachment is considerably assisted by the sharp air current existing there. The thread may on occasion come into the reach of the blades 5 themselves but if this occurs it will be broken up and torn by the latter.

When the thread x has reached its bottom position and has been detached, it is seized by the blast of air from the fan, which at that point enters the annular space 7 substantially tangentially, and is guided, in accordance with the arrows in Figure 2, upwards on the outer surface of the annular space, whereby it is brought past the outlet connection. The particles, particularly threads or the like, thus perform in the annular space 7 a double circling movement, namely firstly a circular movement about the fan axis and additionally thereto a whirling movement about the annular axis of the air guide space. These two movements, which reciprocally influence one another, in conjunction with the force component P acting in the sense of a displacement of the thread, achieve the effect that even long threads are carried around in a circle until they are completely broken up and torn apart and are able to escape into the dust collector. The whirling of the air current provides the additional advantage that, precisely in the case of threads of similar long particles, twisting-up and balling-up are brought about, which likewise promote the escape of the threads through the discharge connection.

As already mentioned, the embodiment illustrated is only given by way of example and the invention is not restricted thereto. On the contrary, many other constructions and applications are possible.

l claim:

1. A suction head for a vacuum cleaner or the like, comprising, in combination, a circular housing having a central axis and being constituted by a front portion and a rear portion, said front portion being constituted by a pair of spaced inner and outer frusto-conical front walls forming between themselves a substantially frusto-conical front chamber, said inner front wall having an angle of taper which is of such magnitude that said inner front wall is slightly less than normal to said central axis and said outer front wall being formed with central opening means constituting an inlet into said front chamber, said rear portion being constituted by a pair of inner and outer rear walls, said inner rear wall being frnsto-conical and said outer rear wall being substantially J-shaperl, joining said inner rear wall at the larger edge thereof and being a continuation thereof so that said inner and outer rear walls form between themselves a rear chamber of substantially U-shaped cross-section having a continuous inner surface including an innermost frusto-conical surface portion, said inner rear wall tapering toward said inner front wall and joining the larger edge thereof along a junction spaced slightly from the smaller edge of said inner rear wall so that the small end portion of said inner rear wall is free and forms an annular nose projecting into said front chamber, said inner rear wall having an angle of taper which is inclined in the same direction as the angle of taper of said inner front wall and which is of such magnitude that said inner rear wall approximates a cylinder, so that said inner front and rear walls form with each other an angle slightly greater than said outer rear wall joining said outer front wall at the larger edge thereof and being a continuation thereof so that said front and rear chambers are in communication with each other; outlet means formed through said outer rear wall; and frusto-conical blower means arranged in said front chamber for drawing air thereinto through said inlet and for moving the drawn-in air into said rear chamber, said blowermeans including a frusto-conical body portion adjacent said inner front wall and being substantially flush with said annular nose, and frustoconical blade means traversing the remainder of said front chamber, whereby particles in air drawn into said inlet means by said blower means are subjected to a substantially radial blower force exerted thereby and are thus centrifuged into said chamber against said outer rear wall so that at least some particles may move over at least a portion of said continuous inner surface of said rear chamber and thereafter directly into said outlet means and so that other particles may move past the joint of said inner and outer rear walls and over said innermost frusto-conical surface portion of said rear chamber in substantialiy axial direction toward the joint of said front and rear chambers so as to be re-subjcctcd to the substantially radial blower force exerted by said blower means.

2. A suction head for a vacuum cleaner or the like, comprising, in combination, a hollow housing having a central axis, an axially extending tubular inlet, and a frusto-conical outer front wall having a smaller open end joined to and forming a continuation of said inlet and a larger open end spaced from said inlet, said housing further including an annular channel of substantially U-shaped cross section surrounding said central axis, having its interior directed toward said outer front wall, and

5 having an outer annular channel wall joined to and forming a continuation of said larger end of said outer front wall, said outer channel wall having a concave inner face, and said channel having a substantially cylindrical but slightly frusto-conical annular inner channel wall which decreases in diameter as it approaches said outer front wall and which terminates short of the latter to form therewith an annular entrance gap leading into said channel, said housing including a frusto-conical inner front wall almost normal to said central axis, coaxial with and inclined in the same direction as said outer front wall and being axially spaced from the latter to define therewith an annular frusto-conical chamber communicating with said inlet and the interior of said channel, and said inner front wall having an outer periphery joined to said inner channel wall adjacent to but spaced from the end thereof nearest said outer front wall thus providing in the interior of said housing an annular lip formed by the end of said inner channel wall nearest said outer front wall; an outlet fixed to said outer channel wall, communicating with the interior of said channel, and extending radially with respect to said central axis; and an impeller carried by said inner front wall for rotation about said central axis, overlapping said lip, and located in said frusto-conical chamber for sucking air along said inlet into said latter chamber and for driving the air into said channel in one axial direction along said inner concave face of said outer channel wall and then around inwardly toward said central axis and in an opposite axial direction along the inner face of said inner channel wall to create air currents directed into the interior of said channel away from the inner surface thereof and moving to said outlet, whereby foreign particles on the inner face of said inner channel Wall will be removed therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,042,506 DeVollat Oct. 12, 1912 2,040,188 Smellie May 12, 1936 2,463,976 Kilchenmann Mar. 8, 1949 FOREIGN PATENTS 388,267 France Oct. 7, 1908 419,176 Great Britain Nov. 7, 1934 579,780 Great Britain Aug. 15, 1946 

